Introduction to Evolution

1. Introduction to Evolution • Question #1 • What is your definition of evolution? • This is your definition, not anyone else in class. • Take about 2 minutes to think about what you are going to write (don’t write anything yet!). • Take 2-3 minutes to write your definition on a blank piece of paper.

2. Introduction to Evolution • Evolution can be described as “change over time”. • The evolutionary process is by which modern organisms have descended from ancient organisms.

3. Introduction to Evolution • Our definition of evolution: • The change in allele frequency (genetic make-up) in a population over time. • This can be caused by many factors in which we will discuss later.

4. Introduction to Evolution • Question #2: • Did humans evolve from monkeys? Explain.

5. Introduction to Evolution • Explanation: • Humans did not evolve from monkeys. • Humans are more closely related to modern apes than to monkeys, but we didn't evolve from apes, either. • Humans share a common ancestor with modern African apes, like gorillas and chimpanzees. • Humans are probably most closely related to two chimpanzee species: the common chimpanzee and the bonobo.

6. Introduction to Evolution • Scientists believe this common ancestor existed 5 to 8 million years ago. • Shortly thereafter, the species diverged into two separate lineages. • One of these lineages ultimately evolved into gorillas and chimps, and the other evolved into early human ancestors called hominids.

7. Introduction to Evolution • We are not the king of all species. • We all come from ONE common ancestor.

8. Introduction to Evolution • Key points to understanding the process of evolution: • This is not a religious topic. • This is a theory that is well-supported. • Remember, this is the explanation of a process that happens (and has been happening) to all biological organisms. • Have an open mind!!!!!!!

9. Charles Darwin • The individual who contributed more to our understanding of evolution than anyone was Charles Darwin.

10. Charles Darwin • Born in England in 1809 (same day as Abraham Lincoln). • In 1831 set sail from England around the world on the HMS Beagle. • This would become one of the most important voyages in the history of science.

11. Charles Darwin • During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time. • That hypothesis, now supported by huge body of evidence, has become the theory of evolution.

12. Charles Darwin • On this voyage, Darwin made many stops and observed and collected many species of plants and animals. • He began to realize that an enormous number of species inhabited the Earth.

13. Charles Darwin • Darwin was intrigued by the fact that all species were so well adapted to whatever environment they inhabited. • He was also fascinated by the many ways organisms survived and produced offspring.

14. Charles Darwin • Darwin was also puzzled by where different species lived and did not live. • Australia and Argentina have the same grassland ecosystem but are inhabited by completely different animals. Ring-tailed Coati

15. Charles Darwin • For Darwin, these patterns posed challenging questions: • Why were there no rabbits in Australia (yet) despite the perfect habitat? • Similarly, why were there no kangaroos in England

16. Charles Darwin • Darwin soon realized that living animals represented just part of the puzzle posed by the natural world. • Darwin collected many fossils on his voyage. • Some resembled organisms that were alive. • Some looked completely unlike any creature ever seen.

17. Charles Darwin • As Darwin studied fossils, new questions arose: • Why had so many of these species disappeared? • How were they related to living species?

18. The Galapagos Islands • These island locatedabout 1000km west of South America influenced Darwin more than any stop made during his voyage.

19. The Galapagos Islands • These island are located very close together but have completely different climates and ecosystems. • The smaller, lower islands are hot, dry, and barren of most vegetation. • The bigger, higher islands have greater rainfall and a higher abundance of plants and animals.

20. The Galapagos Islands • Darwin was fascinated with the land tortoises found in the Galapagos. • Darwin learned that these tortoises varied in predictable patterns from one island to another.

21. The Galapagos Islands • The dome-shaped shell tortoises are found on wetter islands such as Isabela. • The intermediate shell tortoise are found on islands with a mixture of dry and vegetative ecosystems. • The saddle-backed tortoises are found on drier islands such as Hood. • Why?

22. The Galapagos Islands Saddle-Backed Tortoise

23. The Galapagos Islands • Darwin also examined many different types of brown birds foraging for seeds. • He noted a difference in beak shapes on many of these birds and thought they were all different species of brown bird (wrens, warblers, etc) at first.

24. The Journey Home • While heading home, Darwin spent a great deal of time thinking about his findings. • Darwin had observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos.

25. The Journey Home • After returning to England, Darwin began to wonder if animals living on different islands had once been members of the same species. • According to this hypothesis, these separate species would have evolved from an original South American ancestor species after becoming isolated from one another.

26. The Journey Home • Was this possible? • If so, it would turn people’s view of the natural world upside down.